In recent years, a server device which provides a game via a network has spread. The game provided by the server device includes one in which a plurality of users can participate (a so-called “social game”), in which the users can not only battle and cooperate with each other but also communicate with each other (for example, refer to Patent Document 1).
However, such a game only allows users to cooperate with each other, etc., and there is not a game which can provide a synergetic effect beyond expectations and increase users' interest.